Abstract P5-15-05: The impact of a change in margin width policy on rates of re-operation for breast conserving surgery

Abstract

Abstract Background: The definition of a negative surgical margin in prospective randomized trials of breast conserving surgery (BCS) is ‘no tumour at ink’ with no conclusive evidence that wider margins of 1mm, 2mm or 5mm are essential for optimal outcomes in the era of modern radiotherapy techniques and systemic therapy. Our group have previously shown that residual tumour is present in only 6% of specimens when re-excision is prompted by a margin of 2 – 5mm compared with 40% for when primary tumour margins are ≤2mm. An audit was undertaken to determine the effect of a change in margin mandate from 5mm to 2mm on rates of re-excision and residual disease in re-excision specimens. Methods: Data were collected retrospectively from 410 women undergoing BCS for symptomatic and screen-detected invasive and non-invasive disease between November 1st 2009 and October 31st 2011. Rates of re-excision and residual disease in re-excision specimens were compared for 215 patients in the 12 months immediately before (Group 1) and 195 patients in a similar time period after (Group 2) a change in margin policy. All impalpable lesions had conventional intra-operative specimen imaging. Statistical analysis was performed using Fisher's exact test. Results: Amongst these 410 BCS patients, there were similar proportions of symptomatic and screen-detected cases in each group, but slightly more wire-localized procedures in group 2 (59.5% versus 48.4%; p = 0.029). Rates of patient re-excision were 21.9% (47/215) for group 1 and 25.6% (50/195) for group 2 with no significant difference between margin mandates of 5mm and 2mm respectively (p = 0.42). Eleven patients in each group had a completion mastectomy with 6 and 4 patients in Groups 1 and 2 respectively undergoing >1 re-excision. There was a trend for an increased proportion of residual disease following a change in margin policy (30.2% group 1, 40.7% Group2; p = 0.32) and the majority of re-excision cases had ductal carcinoma in situ alone or combined with invasive cancer in the primary specimen (>80%). There was no significant difference in the proportion of wire-localizations for all re-excisions (≥1) between Group 1 (31/42 = 74%) and Group 2 (25/43 = 58%) (p = 0.17). Conclusion: A reduction in target surgical margin width from 5mm to 2mm has not decreased rates of re-excision but yields a trend towards an increase in proportion of specimens with residual disease. Longer follow up is required to assess rates of local control and further analyses will ascertain whether a less stringent margin policy is more appropriate for contemporary BCS where adjuvant treatments contribute to local control. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-15-05.